Sharpless Assymetric Epoxidation Reaction

Sharpless Assymetric Epoxidation Reaction - AE-DETAE(–-...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: AE-(+)-DETAE-(–)-DETR2R3R1OHR1R3R2HOOHCH3OHOCH3R2R3R1OHOEtO2CCO2EtOHOHOHOCH3PhOHOOHOPrOHOC7H15OHOCH3OHBnOOOHOCH3PhOHOH3CCH3CH3OHCH3PhPhOOHOH100OHOHOHOHOH14OHChem 215Sharpless Asymmetric Epoxidation ReactionMyersTi(Oi-Pr)4,(+)-DETt-BuOOH, 3Å-MSCH2Cl2, –20 °C• 10-20 mol% excess tartarate vs. Ti(OiPr)4required.• (+)- and (–)-DET are readily available and inexpensive.•Z-disubstituted olefins are least reactive and selective.• 5-10 mol% catalyst in the presence of 3 or 4 Å-MS.Mnemonic for selectivity:Asymmetric Epoxidation of Allylic Alcohols:Application of Mnemonic:8988799574Examples of Sharpless Epoxidation:productee (%)65From: Gao, Y.; Hanson, R. M.; Klunder, J. M.; Ko, S. Y.; Masamune, H.; Sharpless, K. B. J.Am. Chem. Soc.1987,109, 5765-5780 and Johnson, R. A.; Sharpless, K. B. In CatalyticAsymmetric Synthesis, Ojima, I., Ed.; VCH: New York, 1993; pp. 103-158.L-(+)-DET "O"D-(–)-DET "O"yield (%)90>989586>9891Reviews:Katsuki, T.; Martin, V. S. Org. React.1996,48, 1-300.Johnson, R. A.; Sharpless, K. B. In Catalytic Asymmetric Synthesis, Ojima, I., Ed.; VCH: New York,1993, pp. 103-158.Johnson, R. A.; Sharpless, K. B. In Comprehensive Organic Synthesis, Trost, B. M.; Fleming, I., Eds., Pergamon Press: New York, 1991,Vol. 7, pp. 389-436.Pfenninger, A. Synthesis1986, 89-116.8080Substitution patterns:9094tartarate (%)h23112920.755• (+)- and (–)-DIPT, diisopropyl tartarate, are also available and sometimes lead to higherGao, Y.; Hanson, R. M.; Klunder, J. M.; Ko, S. Y.; Masamune, H.; Sharpless, K. B. J. Am. Chem. Soc.1987,109, 5765-5780.97%, 86% ee97%, 86% ee(+)-DET =Katsuki, T.; Sharpless, K. B. J. Am. Chem. Soc.1980,102, 5974-5976.selectivity.Ti(%)(+)-DIPT (6.0)(+)-DIPT (7.5)(+)-DET (5.9)(+)-DET (14)(+)-DIPT (7.5)(+)-DET (142)(+)-DET (7.4)(–)-DET (150)554.71055120°C–20–12–10–35–20–20–20M. MovassaghiChiral Substrate:...
View Full Document

This note was uploaded on 04/07/2008 for the course CHEM 215 taught by Professor Shair during the Fall '07 term at Harvard.

Page1 / 4

Sharpless Assymetric Epoxidation Reaction - AE-DETAE(–-...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online